ISHS Acta Horticulturae 766: XXVII International Horticultural Congress - IHC2006: International Symposium on Ornamentals, Now!
ASPECTS OF CO2 UPTAKE IN THE CRASSULACEAN ACID METABOLISM ORCHID PHALAENOPSIS |
| Authors: | S. Ichihashi, T. Higuchi, H. Shibayama, Y. Tesima, Y. Nishiwaki, K. Ota |
| Keywords: | photosynthesis, CAM, relative humidity, temperature, light, irrigation |
| DOI: | 10.17660/ActaHortic.2008.766.33 |
| Abstract:
Phalaenopsis and its hybrids are the most important orchid pot plant com¬mercially in the world now. Research on photosynthesis gives us practical and useful information for improving cultivation. Although conventional gas-exchange technique has some limitations in the research of a crassulacean acid metabolism plant (CAM), we investigated CO2 uptake in Phalaenopsis. CO2 uptake at night (Phase 1) changed with temperature. Maximum CO2 uptake was observed around 20°C. CO2 absorption at night increased in proportion to CO2 concentration. Rate of CO2 absorption was higher at 20°C than at 25°C. CO2 uptake in the late afternoon (Phase 4) showed a maximum around 20°C. CO2 absorption in Phase 4 increased in proportion to CO2 concentration but stomata conductance decreased under high CO2 levels. CO2 absorption response curve to light intensity in Phase 4 was not saturated till 500 µmol.m-2.s-1 PPFD when CO2 level was 2000 ppm, and then the stomata conductance showed very low values. Under various water and humidity condition when Phalaenopsis was irrigated weekly, CO2 uptake in Phase 1 was the largest at one day before watering, but that of Phase 4 was the largest at one day after watering. Total CO2 uptake in all Phases was stimulated the most at 70% relative humidity and suppressed drastically at 30% relative humidity. These results indicated that higher relative humidity was likely the most important factor for high CO2 absorption in Phalaenopsis. | |
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